It has been 4 months since applied for N400 no biometrics yet ?

This is normal and you must be patient for scheduling.

Yes it is possible although more likely a normal delay.

Can a LPR for 3,5 years, that was initially sponsored qualify for a USCIS form 131 fee waiver if not claimed in sponsors tax.

You can try to apply and worst case is a rejection.

What documents should I submit?

Yes this appears appropriate for renewal purposes. Refer to form instructions for further guidance.

No this alone should not impact your adjustment eligibility.

Can i file I-130 for my sibling

You may file for her with your parents pending case. It will take 12-15 years for her visa to become current.

How long does it take to get biometric appointment after 65days of filling in and when should I expect my EAD?

EAD processing is currently delayed so best to refer to USCIS webpage directly for current processing times.

You should contact USCIS to inquire about rescheduling.

My husband has an green Card can he sponsor me?

Yes assuming you entered the US with valid status and you have maintained valid status.

How can speed up the appointment for my husband what can I do?

You may contact the Consulate directly to inquire about delays and processing times.